1. Field Invention
This invention relates to the axial shifting and crossing of work rolls in a hot or cold rolling mill, wherein, each roll chock is supported by a pair of Mae West blocks which are mounted in the mill housing. Between the chocks and the corresponding Mae West blocks there is defined a pair of contact surfaces whereby, during axial shifting of the work rolls, work roll chocks are caused to slide along the supporting Mae West blocks, thereby causing accompanying simultaneous crossing of the rolls as a result of movement of the roll chocks in a direction perpendicular to the roll axis.
2. Description of the Prior Art
In conventional rolling, with parallel, cylindrical rolls, the rolls wear unevenly along the roll barrel length. Also, deviations in roll configuration, due, for example, to uneven roll wear and distortions caused by thermal conditions to which the rolls are exposed, cause unwanted deviations from a desired flat condition of a workpiece, such as sheet or strip, being rolled. For example, such rolls develop edge grooves which produce ridges on the rolled workpiece.
The normal purposes of axial shifting of rolls in a rolling mill are (1) to control workpiece profile, and (2) to distribute roll wear more evenly.
One example of relatively new and advanced prior art roll shifting is the so-called controlled variable crown, or CVC, rolling in which the work rolls and backup rolls have an S- or bottle-shaped profile and which provides for adjustment of the roll gap profile by bidirectional shifting of the rolls, e.g. in compensation of thermal changes. Disadvantages of the CVC system are that it requires special, asymmetrical roll grinding, and produces an asymmetrical backup roll wear pattern. Moveover, it does not provide sufficient improvement to avoid the need for use of several sets of rolls for rolling a range of sheet or strip of various sizes which can be rolled in a given mill.
Roll crossing is used to modify the roll gap profile for control of the flatness and profile of a rolled workpiece and, as such, competes with roll shifting processes and apparatus such as the CVC system. Presently, roll crossing in rolling mills is performed by actuators that apply displacement forces to the roll chocks in a direction perpendicular to the roll axes. These forces have opposite directions for the chocks of the drive and operator sides of the mill and are applied either directly to the chocks or through equalizing beams. Typical actuators are of a screw-nut or hydraulic mechanism type. The main deficiency of such systems is their complexity. There are three main types of cross-rolling: (1) crossing of the work rolls only; (2) pair crossing--crossing of both work and backup rolls, and (3) crossing of backup rolls only. Crossing of the work rolls only is the least expensive approach; types (2) and (3) are both expensive, although type (2)--pair crossing is the most commonly used.